In the wording of the problem, I don't think it is a good idea to use the letter n for two different variables - first as the index of the sequence, then as an element of T. I think it would be better to change the second use to a variable named t for example.

I'm wondering if someone would be willing to give me a prime that is part of a triple but not on my list. That would help me to figure out if the issue is with how I'm generating/determining my primes or with how I'm looking for triples.

https://projecteuler.net/about=aliases If you hover over a poster's name in a solution thread (specifically the ones that are in italics, which indicates it is an alias), you will see a tooltip showing the account username. Unfortunately the quoting system always seems to display the username, not i...

The wiki page on sorting algorithms has a separate section for non-comparison integer sorts like this. Its main disadvantage is that its running time and its memory requirements depend on max, not just on n.

If you ever need more than, say, 600MB of data, then you are probably doing it wrong. You are either using the wrong solving method, or maybe you just don't need to have all of that data in memory at the same time.

Cheers Jaap, I'm afraid I'll have to confess my ignorance on the first question (I'll google that though). I do use vectors, yes, but I would have thought it would pose problems of efficiency too as it will take up a lot of memory. I'll try that approach over the weekend though and see what happens...

On my system and using C/C++, defining an array this size immediately causes a 'Segmentation fault' - and the number spaces required only get larger on some of the more difficult problems on PE. Am I missing something? Do you know the difference between the stack and heap memory? Do you know how to...

Oh, it's the unmistakable work of Raymond Smullyan. The strings we are working with are expressions. Just like an ordinary arithmetical expression like "4+5" can be evaluated to yield "9", these strings have their own type of arithmetic that can be used to evaluate them and yield another string. You...

Main.java:2: error: class aUVa100 is public, should be declared in a file named aUVa100.java It IS "declared in a file named aUVa100.java" but... I don't know the online IDE/compiler this site uses, and I don't think I can access it without becoming a member. It clearly thinks it is in a file calle...

... hence $\sin 4x=\sin 3x$ implies $\sin(\pi-4x)=\sin 3x$ Nicely done. This is the trick that I missed. I thought we would have to go all the way up to $\sin(7x)$, which would be horrible. NOTE: All this in hindsight knowing that n should be 7. To derive it in an Olympiad is close to impossible fo...

So people here can't solve an Olympiad question I probably could but I can't be bothered. Spending a couple of minutes here and there during breaks at work is rather different from actually solving it in Olympiad. Olympiad questions are often hard until some specific insight hits you, and it can ta...